1. Field
This invention relates to an external anti-inflammatory and analgesic agent. More particularly, it is concerned with an external anti-inflammatory and analgesic plaster preparation wherein a salt of diclofenac with a cyclic organic base is contained as an active ingredient and release and absorption are remarkably improved.
2. Prior Art
Where various non-steroidal anti-inflammatory and analgesic agents are orally administered, an efficient drug distribution in inflammatory sites is difficult to be achieved and further undesirable side-effects could be produced in gastrointestinal tracts in such diseases developed relatively locally near body surface as arthritis, sarcitis, tenovaginitis and the like.
Accordingly, there have been developed in the field of orthopedics ointments containing various non-steroidal agents in order to avoid systemic side-effects and they have been medicinally supplied as a practical pharmaceutical preparation. Also, there have been proposed plaster preparations as another pharmaceutical preparation having the same efficacy. The plaster preparation could have many advantages not seen in the ointments, such as prolonged effects, precise dosages, simple administration, cooling effects on diseased parts by the free water involved in the base and fixing effects on diseased parts by the preparation. Presently, there have been supplied those plaster preparations containing three sorts of non-steroidal agents, indomethacin, Ketoprofen and flurbiprofen and their usefulness has been appraised. However, these agents have an extremely low solubility in water and thus it is essential to add a specific drug solubilizer or solubilizing agent.
On the other hand, Japanese Patent Kokai Koho No. 63-152372 discloses a salt of diclofenac with an organic cyclic base and a pharmaceutical composition containing same, in which it is reported that the pharmaceutical compositions containing the diclofenac salt are effective as an anti-inflammatory and analgesic for oral administration.
Hitherto, there have been used external anti-inflammatory and analgesic plaster preparations of a diclofenac type containing diclofenac-Na salt as an active ingredient. Since the diclofenac-Na salt has a low solubility to water so that a skin permeability is reduced and therefore, a sufficient pharmacological effect can not be obtained when applied to the skin.
For overcoming such disadvantages, there have been provided various improvements in the external diclofenac-containing plaster preparations. As disclosed in, for example, Japanese Patent Kokai Koho Nos. 57-24308, 57-81409, 60-208909, 61-60608 and 62-181226, there are provided the external anti-inflammatory and analgesic plaster preparations having added a dissolution assistant to raise the solubility of diclofenac Na-salt or having an absorption accelerator to raise the permeability to skin.
However, there are problems that the addition of the dissolution assistant or absorption accelerator results in loss of freedom in a design for preparation and also, the skin subjected to treatment is injured by the dissolution assistant or absorption accelerator used.
Accordingly, an object of the present invention is to provide an anti-inflammatory and analgesic plaster preparation having a sufficient pharmacological effect with good absorption to skin and prolonged effects in respect of the diclofenac-containing anti-inflammatory and analgesic plasters which were regarded as difficult for preparation.